1. Technical Field
The present invention relates, in general, to an improved wireless communications system. In particular, the present invention relates to a method for updating billing information associated with a mobile subscriber unit. Still more particularly, the present invention relates to a method for dynamically updating billing information for a mobile subscriber unit when a long distance call is delivered to the mobile subscriber unit.
2. Description of the Related Art
A cellular telephone system typically includes mobile subscriber units that may be mobile or portable, and cellular base stations that are connected to the public telephone company via one or more cellular switching networks. Each cellular subscriber has an assigned cellular telephone number that allows the user to place and receive calls within a widespread range of the cellular base stations, such as throughout a metropolitan area. Cellular telephone systems are thus based on a structure of associated cells. Each cell constitutes a specified geographic area that (a) is defined for a specific mobile communications system; and (b) has its own base station and a single controller interconnected with a public telephone network.
In existing radio telecommunications networks, billing information is not immediately available to subscribers. Typically a call may span several mobile switching centers (MSCs), and toll ticketing (TT) records are generated in each MSC which participated in processing the call. Once the call is completed, the TT records from each MSC are stored on a hard disk memory device for that MSC. Once a day, or once a week, whatever an operator's practice may be, the TT records may be backed up on magnetic tape. In addition, the TT records may be transferred via a data-transfer portal (an X25 or TCP/IP portal for example) within the MSC to an external billing center for post processing. The external billing center may belong to a particular operator and may process only that operator's TT records, or the center may process records from several operators. Operators who have their own post-processing facilities generally transfer their TT record files via a dedicated link from the MSC to their local post-processing facility. Once in the billing center, the TT records are processed and billing information is generated and sent to the respective operators. The billing information is then utilized to settle accounts between operators for automatic roaming services and to bill individual subscribers.
Users often desire to make toll calls via mobile communication devices, such as cellular telephones. In public switched telephone systems, including those that incorporate mobile cellular telephone systems, a toll is a charge for a connection to a central office or a user end instrument that is beyond a call originator exchange boundary. The amount of a toll (i.e., toll call) is usually based on various factors, such as distance, the number of exchanges utilized, duration of the call, time of day, locations of call originator and call receiver, type or class of service, and extent of utilization.
When a mobile phone is called, a gateway mobile switching center (G-MSC) obtains a Temporary Location Directory Number (TLDN) from a serving mobile switching center (S-MSC) for the purpose of routing the call to the mobile. The wireless customer is typically billed for toll charges from the originating rate center to the terminating rate center. However, the TLDN does not necessarily indicate the rate center in which the terminating mobile is located. In order minimize trunk backhaul and simplify allocation of TLDNs, it is common practice to assign a TLDN from the rate center in which the S-MSC is located, not the rate center in which the mobile telephone is located. For example, a switch located in Vancouver would assign a Vancouver TLDN but the mobile itself could be located on a cell site in the interior region of British Columbia, hundreds of miles from the city of Vancouver.
If the home carrier wants to know in which rate center a mobile was located on an incoming call, the home carrier must wait for the serving carrier to send this information. This information typically takes more than a month to pass through a "clearinghouse". Hence, the subscriber gets billed for calls received outside his home network several months after the calls were actually placed to the mobile. Subscribers may forget about calls they received months ago and dispute charges. Moreover, delayed billing results in delayed revenue for the subscriber's carrier.
From the foregoing it can be appreciated that a need exists to provide a method and system to send back the last known serving rate center from the S-MSC to the G-MSC so that the home carrier can record the serving city for incoming calls to the subscriber on the subscriber's billing statement and ensure more accurate toll billing for incoming calls to mobiles.